New Collection

It's probably a gold stater of Philip 11 of Macedon.
Apollo facing right (obv.) biga (rev.)
It's been in my collection since 1978.

There's a pretty strong ancient base in the ancient coin forum.

As far as most rewarding it's going to largely depend on what you enjoy which can take some time to figure out and change over time. Budget will play a role too for what's doable and what isn't.

A Type set is usually a rewarding set for people from the amount of time and effort it takes to complete one. It's a great way to get exposure to a lot of different series and figure out which ones you really like too.

For me coins that are harder to find are the most rewarding. They're more frustration and the searching can get old coming up empty over and over but in the end that effort makes the coin that much more enjoyable when you find it. Things that are easy while enjoyable don't provide that same sense of accomplishment when you get them.

As far as your initial question of high end versus getting any old ones budget will again be a big factor for that. A mix of both can be a good way to still get things when the budget is low but quality is always desirable.